I had a 6' vinyl fence installed. It has 5"x 5" vinyl posts.
I want to top the posts with lights.
First I thought about low voltage lights then when I think of wiring 24 posts I thought of solar.
Most of the solar landscaping lights I have seen are pretty pathetic as far as longevity and service life.

Any tips or product recommendations would be appreciated.

I have had luck with the $6 ones from Home Depot. Available in black or white. They are 4x4 but may be adaptable.

I got this one from Lowes which worked great and allowed better coverage for the game camera at night. It lasted about a year until someone stole it.

They also have ones for 5x5 posts.

https://www.lowes.com/pd/Class...k-Post-Cap/999972678

All I have had are JUNK in no time at all!

Putting ~21 lights around my pool deck right now. Mostly just for ambient lighting, but enough to make it safe walk around... I wanted the ability to turn them on and off at will, and possibly dim them, so I am going low voltage.
I got some little / cheap LED's Each light is only .6 watts or ~7 lumens, I may be able to skip the dimmer.

One thing I noticed about those post top lights, some shine straight out mostly... as in, in your eyes, but some shine mostly downward. And then there are the ones that mount on the side of the post rather than the top.